1. Field of the Invention
The present invention relates in general to molds or dies constructed of epoxy resin which are used for molding plastic articles or pressing metal plates. More specifically, the present invention is concerned with durable epoxy resin molds particularly suitable for use in an injection molding which subjects the molds to very high injection pressure. Furthermore, the present invention relates to methods of producing the molds and the dies.
2. Description of the Prior Art
Nowadays, for easiness in production and shaping, plastic molds have been given wide attention in the field of plastic molding. Usually, as the materials of the molds, thermosetting resins, such as epoxy resin, urethane resin, silicon resin and the like are used. Among them, epoxy resin is the best for the marked hardenability and the excellent properties of the fully cured epoxy resin.
However, the epoxy resin molds hitherto used or proposed have failed to satisfy the need for facilitating the work with which the molds are produced and having a durability which the cured epoxy resin must have. Thus, hitherto, the practical use of the epoxy resin molds has been limited to only the use in a trial molding line.
In fact, since the liquid composition of the epoxy resin has a marked viscosity, the work for pouring the liquid composition into a mold-producing die unit and that for degassing the composition are difficult or at least troublesome. Furthermore, since the composition of the epoxy resin requires a relatively high curing temperature, undesired deformation of a master model, which is used when assembling the mold-producing die unit, tends to occur.
Furthermore, the epoxy resin molds hitherto used and proposed have failed to exhibit a satisfied heat resistance at 150.degree. C. Particularly, the epoxy resin molds could not exhibit a satisfied resistance against the environment in which so-called thermal shocks continuously occur.
In view of the above, various attempts have been made for improving the performance of the epoxy resin molds. Some of the attempts are disclosed in Japanese Patent First Provisional Publications Nos. 63-278808 and 63-270104.
In the former publication, a measure is shown in which various whiskers are used for reinforcing the epoxy resin mold. However, the whisker-mixed liquid composition of the epoxy resin shows a marked viscosity causing a difficulty of the composition pouring work.
In the latter publication, there is shown a method for producing molds which are constructed of thermosetting resins. However, similar to the case of the former publication, the composition used has a marked viscosity and thus makes the above-mentioned composition pouring and degassing works difficult.